High pressure, ambient temperature gas storage and delivery devices have been heretofore suggested for providing attitude independent supply of mixed gasses such as breathable air to a user thereof. Such devices, while in use, have limited gas delivery time, are bulky, and must be operated at extremely high pressures.
Liquid air storage and delivery devices have also been suggested (see U.S. Pat. Nos. 1,448,590, 3,318,307, 3,570,481, 3,572,048, 4,181,126, 3,699,775, 1,459,158, and 3,227,208), but suffer from limited standby time due to oxygen enrichment inherent in such storage, some being unduly complex in an effort to confront this problem, are not attitude independent, and are often quite heavy.
Dispensers for cryogenic temperature elemental and compound gasses (below -175.degree. F.) such as oxygen held for use at supercritical pressure (above 730 psia) have been heretofore suggested (see U.S. Pat. Nos. 3,062,017 and 3,827,246) In such dispensers a heat transfer mechanism (i.e., an electrical heating element or a heat exchanger) is utilized to pressurize the storage vessel having liquid oxygen loaded therein at atmospheric pressure (thus making the dispenser less than desirable as an air supply, where oxygen enrichment could occur while liquid air is in standby storage) for expelling the oxygen.
Pressure sensing is thereafter used to sense the heat transfer needs in the vessel to maintain pressure therein above critical pressure by activating the heating element periodically. Heat exchange is accomplished utilizing at least in part active means separate from the dewar thus encumbering these heretofore known dispensers with complex sensing and activating mechanisms to assure proper heat input. Improvement in such dispensers could thus still be utilized
Liquid cooling garments for body cooling using liquid circulating through a network incorporated in the garment have also been heretofore known and/or utilized (see U.S. Pat. Nos. 3,430,688 and 3,289,748). In at least one case, such a garment has been used with a liquid oxygen converting system to provide an integrated cooling and breathing system (see U.S. Pat. No. 4,024,730).
While the integrated system above described may be effective in some applications, such system fails to provided a compact unit (capable of being carried on one's body) such as might be required by fire fighters or other mobile personnel needing such a system. Such systems require electrical input (undesirable in gaseous environments), rely on manual activation to (control flow rates and thus cooling, and make no use of heat exchange to control system operational parameters other than temperature of the breathable air. Moreover, the oxygen converting systems used therein suffer many of the same drawbacks as heretofore discussed. Further improvement could thus be utilized.